Use of a large triaxial cell for testing conditioned soil for EPBS tunnelling

Laboratory testing of soil conditioning for EPB tunnelling is a common procedure to assess the suitability of the conditioning itself in different tunnel projects, but normally the stress influence is not taken into account. This work describes the behaviour of two different conditioned masses in different stress conditions through a large diameter triaxial cell, which allows to reproduce different stress scenarios. The results obtained show the influence of the stress on the shear strength of the conditioned material and the different attitude of behaving as a fluid testing a granular material and a more heterogeneous one. Also the two material behaved differently as the presence of a more relevant fine part in the conditioned mass allows the material to maintain its fluidity also at higher pressures